1. Field of the Invention
The present invention relates to a holding member for an electrochemical cell, a holding structure of the same and an electrochemical system. The present invention further relates to an electrochemical cell and an electrically conducting member used for connecting it.
2. Related Art Statement
Solid oxide fuel cells are generally divided into two categories; a planar type and a tubular type. In planar type solid oxide fuel cells, a power generating stack is formed by alternately laying so-called separators and power generating layers, (cell). An appropriate structure is needed for separating a fuel gas and oxidizing gas when a plurality of planar single cells are stacked to produce a generator. It is also necessary to reduce the thermal stress between the single cells, manifold for gas supply and separators (interconnectors).
In Japanese Patent Laid-open No. P1993-54897A, an anode and a cathode are respectively formed on each side of an electrolyte to prepare a power generation layer (cell). Then, a thin film containing ceramic powder and an organic binder is sandwiched between this cell and the separator, and the assembly is heat-treated so that the cell and the separator are joined with each other.
Japanese Patent publication P1994-290798A disclosed another type of a solid oxide fuel cell. In the disclosure, a plurality of ring-shaped single cells are stacked to produce a generator. Each of the cells is held with a metal separator. The separator has a disk-shaped gas manifold and a flange portion surrounding the gas manifold. The gas manifold has formed therein two through holes for an oxidizing gas and a fuel gas. The flange portion has formed therein grooves for the oxidizing and fuel gases. The flange portion is intervened between the adjacent single cells vertically arranged. An oxidizing gas is supplied into a mesh through hole in the gas manifold. The supplied gas then flows in the groove in the flange portion and contacts with the cathode electrode of the single cell. A fuel gas is supplied into the other through hole of the gas manifold. The supplied fuel gas then flows in the groove of the flange portion and contacts with the anode electrode of the single cell, so that the gases may contribute to power generation. An insulating plate is interposed between the adjacent separators to prevent the short-circuit between the separators.
Further, in a prior planar type solid oxide fuel cell, a gas sealing portion is positioned in the outer boundary of the cell. For example, FIG. 12 of Japanese Patent publication 1994-290798A shows a perspective view of one of such planar type cell. According to this disclosure, the cell is composed of a plate of a solid electrolyte material, a fuel electrode and an air electrode, each being made of a ceramic material. The cell and separator that are made of ceramic materials are alternately stacked to produce a generator. In the stack, a groove for supplying an oxidizing and a fuel gas are formed crossly.
To produce a generator by stacking separators and single cells alternately, it is necessary to supply a gas between the separator and the cell so that fuel and oxidizing agent may be supplied to the electrodes of the single cell. At the same time, the single cell and the separator must be electrically connected in series by intervening an electrically conductive connecting member between the separator and single cell. When such connecting member is located in, for example, a fuel gas passage, it must be chemically stable in a reductive fuel gas environment at an operating temperature of the single cell. Further, there must be a gap through which the fuel gas is passed. For such reasons, so-called nickel felt has been commonly used as the connecting member in the fuel gas passage.
On page 824 of “Electrochemical Society Proceedings Volume 99-19” is shown a stacked layer of a separator and a planar single cell. A number of elongated passages regularly arranged are formed on the separator and the grooves are used as fuel gas supply passages. A power generation device is formed by sandwiching a mesh between a surface on the separator groove side and an anode electrode film of the single cell and pressing the mesh.
On pages 8 to 9 and FIG. 1 of Japanese Patent Publication No. 503381/2002, a separator and a cell are connected to each other by sandwiching a corrugated sheet between the separator and cell and then by pressing it. The corrugated sheet electrically connects the separator and the cell. Further, the publication describes that the corrugated sheet is preferably made of an expanded metal.